The present invention relates to an organic electroluminescent color display unit. In particular, the invention relates to an organic light emitting diode (herein after referred to as OLED) color display unit having a light emitting layer comprising an organic electroluminescent material.
Recently color display units using OLED attract attention for their superior display performance. However, methods for manufacturing OLED display devices, in which light emitting layers are formed for each of red, green, and blue, are complicated, resulting in high production cost. Further, it is difficult to produce such display units with high resolution and into large area.
In order to solve the problem, a color display unit having only white light emitting layers is suggested. In this case, desired display colors are obtained by using a color filter.
Referring to FIG. 4, a color display unit 51 comprises a color filter structure 53 which comprises color filter elements 53a and a planarization film 53b formed over a glass substrate 52. An anode 54, an organic electroluminescent layer 55 and a cathode 56 are laminated over the color filter structure 53 in succession. A shielding cover 57 for covering these is adhered to the substrate 52. The shielding cover 57 is disposed to shield from ambient air the organic electroluminescent layer 55, which is reactive to oxygen and moisture. A gettering material 57a is accommodated within the shielding cover 57. The gettering material refers to a substance that is disposed for absorbing components, such as moisture and oxygen, that degrades the organic electroluminescent layer 55. An absorbent, a desiccant, or an oxygen absorbent or the like is used solely or in combination.
However, the color filter elements 53a are generally contains an organic pigment. The organic pigment and/or a transparent resin in which the pigment is dispersed contain moisture. Further, the planarization film 53b disposed over the color filter elements 53a also contains moisture. Accordingly, the organic electroluminescent layer 55 was degraded by trace moisture and oxygen that are released from the color filter structure 53 and that penetrated into the organic electroluminescent layer 55. Further the organic electroluminescent layer 55 was also degraded by formation of corrosive gases, such as chlorine gas, in some materials used for the planarization film 53b. 
In active matrix display units, it was necessary to form a thin film transistor (TFT) drive circuit over the color filter structure 53. However, heat generated through production of the thin film transistors damaged the color filter structure 53.
Referring to FIG. 5, Japanese Laid-Open Patent Publication 10-116687 disclosed an organic electroluminescent display unit 61 in which deterioration of organic electroluminescent devices by the above described organic pigments is suppressed. The electroluminescent display unit 61 includes an inorganic color filter 60 between a substrate 52 and a transparent electrode 58 as shown in FIG. 5. The inorganic color filter 60 is disposed at a position associated with an organic electroluminescent device 59 and is covered by a protection layer 62. The protection layer 62 protects the inorganic color filter 60 during an etching process of the transparent electrode 58, as well as planarizes the steps of the inorganic color filter 60.
However, the applicable colors are limited in the case where an inorganic color filter is used. Accordingly, in order to reproduce colors flexibly in a color display unit, it is necessary to use an organic color filter. In such cases, problems of moisture and gas components penetrated from the color filter structure 53 arise as described above.
Further, the color filter has pixels which is respectively colored to red (R), green (G), and blue (B). The steps, which are formed between different colored dyes, are flattened by providing a planarization film formed from resin on the color filter elements. However, the color filter and the planarization film are relatively thick compared to the organic electroluminescent layer. Accordingly, regions that can be a local curvature in comparison with a thickness of a thin organic electroluminescent layer are formed, while the step may not be assumed as a curvature in comparison with a thickness of the color filter and the planarization film. As a result, an anode and a cathode, which are disposed by interposing a thin organic electroluminescent layer, can be short-circuited in the case where the organic electroluminescent device is formed on a planarization film that covered the color filter as disclosed in conventional art. This reduced reliability of the display unit as well as reducing the yield ratio. The problem of the planarization occurs regardless of the use of an organic color filter or an inorganic color filter.